Methods and apparatus to identify media based on watermarks across different audio streams and/or different watermarking techniques

ABSTRACT

Methods and apparatus to identify media based on watermarks across different audio streams and/or different watermarking techniques are disclosed. Example apparatus disclosed herein include a watermark detector to detect a first watermark embedded in a first audio stream, the first watermark including a first source identifier and a first timing identifier, and detect a second watermark embedded in a second audio stream, the second watermark including a second source identifier and a second timing identifier. The disclosed example apparatus also include a controller to associate the first and second watermarks with a media detection event when both (1) the first and second source identifiers match and (2) the first and second timing identifiers are chronologically congruent. The disclosed example apparatus further include a transmitter to transmit the media detection event to a data collection facility.

RELATED APPLICATIONS

This patent arises from a continuation of U.S. patent application Ser.No. 15/994,383 (now U.S. Pat. No. 10,694,243), which was filed on May31, 2018, and which is incorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to watermarking technology, and, moreparticularly, to methods and apparatus to identify media based onwatermarks across different audio streams and/or different watermarkingtechniques.

BACKGROUND

Digital watermarking is a technical field that uses sophisticatedtechniques to embed data in media (e.g., audio, video, and/or imagedata) in a manner that is substantially imperceptible to humans but thatcan be detected and/or extracted at a later point in time such as whenthe media is subsequently accessed or presented. One common purpose forwatermarking is to enable the automatic detection of media as it isbroadcast, aired, streamed, or otherwise provided to audience membersaccessing the media. In particular, watermarks including mediaidentifying information to enable a media monitoring entity to trackwhat media is provided by a media provider may be embedded in the media.Watermarks may be used to identify the content produced by the mediaprovider and/or to identify advertisements presented along with themedia provider generated content.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an example environment in which teachings disclosedherein may be implemented.

FIG. 2 illustrates an example manner in which the media monitor of FIG.1 assigns a series of watermarks detected over time to differentmonitoring tracks.

FIG. 3 illustrates an example manner in which the media monitor of FIG.1 assigns each of the watermarks of FIG. 2 to multiple differentmonitoring tracks.

FIG. 4 is a block diagram illustrating an example implementation of theexample media monitor of FIG. 1.

FIGS. 5 and 6 are flowcharts representative of machine readableinstructions that may be executed to implement the example media monitorof FIGS. 1 and/or 4.

FIG. 7 is a block diagram of an example processing platform structuredto execute the instructions of FIGS. 5 and 6 to implement the examplemedia monitor of FIGS. 1 and/or 4.

In general, the same reference numbers will be used throughout thedrawing(s) and accompanying written description to refer to the same orlike parts.

DETAILED DESCRIPTION

FIG. 1 is an example environment 100 in which teachings disclosed hereinmay be implemented. The environment 100 of FIG. 1 includes one or moremedia provider(s) 102 that provide media (e.g., television programming,on-demand media, Internet-based streaming media, advertisements, music,etc.) to one or more media monitoring sites 104. Often, the mediaprovided by the media provider 102 includes content created by the mediaprovider 102 as well as advertisements created by one or moreadvertiser(s) 106.

As shown in the illustrated example, the media monitoring site 104 isassociated with and/or managed by a media monitoring entity (MME) 108,such as The Nielsen Company (US), LLC, to monitor and/or track mediaprovided by the media provider 102.

In some examples, the media monitoring site 104 includes a receiver 110(e.g., set-top boxes or the like) that receives media from the mediaprovider 102 and transmits the media to a media monitor 112 forprocessing. In the illustrated example, the receiver 110 is tuned to aknown (e.g., designated by the MME 108) channel or station associatedwith the media provider 102. By designating the station or channel inthis manner, the MME 108 can monitor what media is aired on thedesignating station or channel at any particular point in time. In someexamples, media monitoring is implemented to track and/or verify whencontent produced by the media provider 102 is actually aired.Additionally or alternatively, media monitoring is implemented to trackand/or verify when advertisements created by advertisers 106 have beenaired on the designated station or channel.

In some examples, the media monitoring site 104 includes multiplereceivers 110 tuned to different channels (associated with the sameand/or different media provider(s) 102). In some such examples, eachreceiver may also have a corresponding media monitor 112. In otherexamples, a single media monitor 112 may collect and/or process the datafrom more than one receiver 110. Further, in some examples, there may bemultiple media monitoring sites each with one or more receivers 110and/or one or more media monitors 112. More particularly, in someexamples, the MME 108 may establish remote media monitoring sites atdifferent geographic locations corresponding to regions where affiliatedstations broadcast media for the region (e.g., local televisionprogramming, local radio programming, etc.). For purposes of clarity andsimplicity, in the illustrated example, only one media monitoring site104 is shown containing only one receiver 110 tuned to a particularstation or channel associated with one media provider 102.

In the illustrated example, the media monitor 112 processes the mediareceived by the receiver 110 to generate media monitoring data that issubsequently transmitted to a central data collection facility 114associated with the MME 108. In some examples, the media monitoring datais generated based on watermarks embedded in the media.

Watermarking refers to techniques used to identify media such astelevision broadcasts, radio broadcasts, advertisements (televisionand/or radio), downloaded media, streaming media, prepackaged media,etc. Existing watermarking techniques identify media by embedding codes(e.g., a watermark), such as media identifying information and/or anidentifier that may be mapped to media identifying information, into anaudio and/or video component having a signal characteristic sufficientto hide the watermark. As used herein, the terms “code” or “watermark”are used interchangeably and are defined to mean any identificationinformation (e.g., an identifier) that may be transmitted with, insertedand/or embedded in the audio or video of media (e.g., a program oradvertisement) for the purpose of identifying the media or for anotherpurpose such as tuning (e.g., a packet identifying header). As usedherein “media” refers to audio and/or visual (still or moving) contentand/or advertisements delivered in any suitable manner (e.g., broadcast,streaming, on-demand, etc.). To identify watermarked media, thewatermark(s) are extracted and compared to reference watermarks and/orother metadata that are mapped to media identifying information.

In many instances, a watermark includes both a source identifier (SID)and a timing identifier (collectively referred to herein as mediaidentifying information) to uniquely identify the media in which thewatermark is embedded. The SID, as its name implies, identifies thesource of the media. For example, the SID may identify a particularmedia provider 102, a particular station or channel provided by themedia provider 102, a particular streaming service associated with themedia provider 102, and/or a particular advertiser 106. Moreparticularly, in some examples, the SID may identify a particularwatermark encoder provided by the MME 108 to the corresponding mediaprovider 102 or advertiser 106. The MME 108 maintains a database of allSIDs at the data collection facility 114 so that each time a watermarkwith a particular SID is reported to the data collection facility 114,the MME 108 can look up the SID to identify the associated source ofmedia (e.g., media provider 102, advertiser 106, particular encoder,etc.).

The SID by itself may be insufficient to uniquely identify media becausemultiple different media items may be encoded with watermarks using thesame SID. Accordingly, watermarks also include a timing identifier. Insome examples, the timing identifier is a timestamp that indicates theparticular time when the watermark was embedded into the media. Forpurposes of explanation and clarity, a timestamp corresponding to thetime when a watermark is encoded into media is referred to herein as an“encoding timestamp.” This is in contrast to a timestamp generated bythe media monitor 112 when a watermark is detected and/or extracted fromthe media. A timestamp generated at the time a watermark is detected isreferred to herein as a “detecting timestamp.” Encoding timestamps areoften used in watermarks encoded into media content produced by mediaproviders 102 at the time of airing of the media. In this manner, theencoding timestamp serves to indicate the actual time when thecorresponding media was aired.

In other examples, the timing identifier may be a unique value known asa time-in-content (TIC) number that corresponds to a particular timewithin the media into which the associated watermark is encoded.Different TIC numbers may be designated for different times within themedia spaced at periodic intervals (e.g., every second, every twoseconds, etc.). Thus, while TIC numbers do not indicate the actual timeof encoding (as with an encoding timestamp), they may still indicate asense of time relative to one another. Furthermore, different TICnumbers are used for each different media item encoded using the sameSID such that, when a watermark is detected, the particular media itemcontaining the watermark and the time within the media item can bedetermined by looking up the SID and associated TIC number. TIC numbersare often used in advertisements because the time of airing is typicallynot as important as for media content created by media providers becauseadvertisements are usually aired multiple times over the course of anadvertising campaign. While encoding timestamps and TIC numbers provideslightly different information, examples disclosed herein may beimplemented using watermarks including timing identifiers that areeither encoding timestamps or TIC numbers.

Typically, watermarks are encoded into media in a manner that isimperceptible to humans. There are multiple different watermarkingtechniques that may be implemented to achieve this result. However, toreduce the likelihood that a human will perceive a watermark, mostwatermarking techniques encode a watermark over a period of time withinthe media. This limits the frequency at which watermarks may be embeddedin media. For example, encoding audio watermarks at a frequencysignificantly greater than approximately once every two seconds islikely to produce an audible sound that may be perceived by humans.

While a watermark every two seconds may be adequate to identifyrelatively long media items, this frequency may be insufficient forrelatively short media items. One reason for this arises from thetechnical complexity in identifying watermarks. While the technicalfield of watermarking used for monitor media is relatively robust andcapable of accurately identifying media, it is still possible that themedia monitor 112 fails to detect a watermark that was embedded in themedia (a false negative). Furthermore, it is not uncommon for a mediamonitor 112 to incorrectly detect a watermark in media when no suchwatermark was encoded (a false positive) based on the content of themedia itself and/or noise in the media signal. False positives produceextra data that has no value (because it has no meaning) that posesprocessing burdens on the devices processing the data as well asincreasing bandwidth requirements at the data collection facility 114 toreceive data associated with the false positives.

One approach to overcoming the limitations of this technology is toidentify media based on the detection of a group of at least twowatermarks. That is, in some examples, a single watermark is notconsidered to be a reliable means to identify media unless it isauthenticated or validated by at least one additional watermark withconsistent media identifying information as the first watermark. A groupof watermarks that is sufficient to reliably identify media is referredto herein as a media detection event. In some examples, a mediadetection event may be based on a group of two watermarks. In otherexamples, a media detection event may be limited to a threshold numberof watermarks that is greater than two.

While defining media detection events to include at least two watermarksmay reduce the impact of false positive detection of watermarks, thisapproach increases the time needed to reliably collect watermarksindicative of media. Furthermore, false negatives increase this timeeven further. For example, if watermarks are embedded at five secondincrements within media, a minimum of ten seconds is needed to establisha media detection event. However, some advertisements are less than tenseconds long such that these advertisements would never be detected.Even if the watermarks were embedded at the effective limit oftwo-seconds apart to provide sufficient time to adequately conceal thewatermark from a human, there is still a need for at least four secondsof media to generate a media detection event, and possibly more if oneor more of the watermarks are not detected (a false negative).

Not any two or more watermarks are grouped together to define a mediadetection event. In some examples, for two watermarks to be groupedtogether as reliably authenticated one another depends upon bothwatermarks having consistent media identifying information (SID andtiming identifier). As used herein, media identifying information fromtwo watermarks is consistent when the SIDs of the watermarks are thesame and the timing identifiers (e.g., encoding timestamp or TIC number)of the watermarks are chronologically congruent relative to a time ofcapture of the associated watermarks (indicated by correspondingdetecting timestamps). For convenience of explanation, watermarks withconsistent media identifying information are referred to herein asconsistent watermarks.

In some examples, the media monitor 112 will generate a detectingtimestamp by capturing a wall-clock value at the time the watermark isdetected. As explained above, this detecting timestamp generated by themedia monitor 112 is distinct from the encoding timestamps correspondingto the timing identifiers in some watermarks. Whereas an encodingtimestamp indicates the time when the watermark was encoded by the mediaprovider 102 and/or the advertiser 106, the detecting timestampindicates the time that the media monitor 112 detected the watermark.Thus, in some examples, timing identifiers (either encoding timestampsor TIC numbers) are chronologically congruent when they are detected inthe same chronological order as the detecting timestamps generated bymedia monitor 112. For example, if the detecting timestamp generated bythe media monitor 112 in response to detecting a first watermark isthree seconds before the detecting timestamp generated in response todetecting a second watermark, the timing identifiers for the first andsecond watermarks may be chronologically congruent if the timingidentifier for the second watermark indicates a later time than thetiming identifier for the first watermark.

In some examples, chronological congruency includes not onlychronological order but also temporal spacing. To use the above example,the timing identifiers for the first and second watermarks may beconsidered congruent only if the second watermark is detected second andwithin approximately three seconds after the first watermark based onthe three second difference between the two detecting timestampsgenerated by the media monitor 112. In some examples, timing identifiersof different watermarks may be designated as chronologically congruentwhen their temporal spacing is within some threshold of variability(e.g., +/−2 seconds) of the temporal spacing of the detectingtimestamps.

Further, in some examples, the chronological congruency between twowatermarks is limited by an upper threshold on the time interval betweenthe watermarks. That is, if the interval between two watermarks exceedsa threshold (e.g., 25 seconds, 30 seconds, 45 seconds, etc.), thewatermarks are not chronologically congruent even if the timingidentifiers follow one another in the correct chronological order andexhibit a comparable temporal spacing to the time of capture (e.g., thedetecting timestamps) of the two watermarks. This threshold is referredto herein as a threshold bridge time. Of course, a series of multiplewatermarks may collectively form a single media detection event thatextends significantly longer than the threshold bridge time so long asthe interval between any two adjacent ones of the watermarks remainswithin the threshold. In other words, in some examples, a newly detectedwatermark is compared against the most recent or last watermark detectedin a series of consistent watermarks for purposes of chronologicalcongruency without regard to earlier watermarks.

Some existing approaches to watermarking detection further limit mediadetection events to watermarks encoded using the same watermarkingtechnique. That is, many types of media include multiple watermarksencoded using different techniques. In the past, only the same type ofwatermarks (e.g., encoded using the same technique) have been comparedto identify consistent watermarks. Thus, two watermarks with consistentmedia identifying information may nevertheless not result in a mediadetection event if the watermarks are based on different watermarkingtechniques.

Further, watermarks are typically compared with other watermarksdetected in the same audio stream. That is, some forms of media providemultiple audio streams corresponding to a single video stream to offeraudio in different languages (e.g., an English audio stream versus aSpanish audio stream) and/or audio in different formats (e.g., stereoversus 5.1 surround sound). In other words, as used herein, differentaudio streams correspond to different representations of audioassociated with the same media item. The different audio streams may betransmitted concurrently with one another (as well as the correspondingvideo stream). Typically, the different audio streams associated with aparticular media item will be separately encoded with watermarks (usingone or more different watermarking techniques). Often, the differentaudio streams are independently monitored so that only consistentwatermarks within a single audio stream are identified to define aparticular media detection event.

The limitations used to define media detection events based onconsistency of media identifying information, watermarking technology,and audio stream is illustrated in FIG. 2. In particular, FIG. 2illustrates a series of thirteen watermarks 201, 202, 203, 204, 205,206, 207, 208, 209, 210, 211, 212, 213 arranged chronologically fromleft to right. In the illustrated example, as media monitor 112 detectsthe watermarks 201-213, the watermarks are assigned to a particularmonitoring track 214, 215, 216, 217, 218, 219, 220, 221, 222. Amonitoring track corresponds to a memory space in which consistentwatermarks are temporarily stored as they are detected. Whenever a newwatermark is detected it is first compared to watermarks in existingmonitoring tracks. If the new watermark is consistent with otherwatermarks in an existing monitoring track, then the watermark isassigned to that track. If the new watermark is not consistent withpreviously detected watermarks in any other track, the media monitor 112generates a new monitoring track and assigns the new watermark to thenew track. As described more fully below, media detection events aregenerated whenever a threshold number of watermarks (e.g., at least two)are assigned to the same track. However, watermarks in separate tracksare not grouped to define a media detection event.

In some examples, the watermarks assigned to a particular track remainassigned to the track only so long as a threshold period of time has notelapsed without a new watermark being assigned to the same monitoringtrack. The threshold period of time corresponds to the threshold bridgetime as described above. Thus, when a new watermark is assigned to a newtrack, a timer is initiated. If a second watermark is detected that isconsistent with the previous watermark before the timer exceeds thethreshold bridge time, the second watermark is assigned to the samemonitoring track and the timer is reset with the possibility thatsubsequent watermarks may be detected and added to again reset thetimer. As described above, once there are two watermarks in the sametrack (or some other threshold number), the watermarks are designated asa media detection event. The media detection event will extend toinclude additional watermarks that are assigned to the same track beforethe timer has elapsed as outlined above. Once the threshold bridge timehas elapsed without another watermark being detected, the mediadetection event (corresponding to as many watermarks as were assigned tothe monitoring track) may be reported to the data collection facility114. Thereafter, the watermarks stored in the monitoring track areremoved so that the monitoring track (e.g., memory space) is madeavailable for a subsequent watermark (or series of watermarks). If thetimer exceeds the threshold bridge time before the second watermark isdetected such that there is only one watermark assigned to the trackwhen the timer elapses, the watermark is discarded and/or disregardingwithout forming a media detection event reported to the data collectionfacility 114. With the single watermark being discarded, the monitoringtrack is cleared out and made available for subsequent watermarks.

In the illustrated example of FIG. 2, there are nine differentmonitoring tracks 214-222 because of the inconsistencies between themedia identifying information in different ones of the watermarks201-213 and/or based on differences in the watermarking techniques usedto encode the watermarks and/or the audio streams in which thewatermarks were embedded. In particular, the parameters associated witheach watermark 201-213 include (as shown in FIG. 2 with reference to thesecond watermark 202) an example source identifier (SID) 224, an exampletiming identifier (TI) 226, an example audio stream 228, an examplewatermarking technique (WT) 230, and an example wall-clock value (CLK)232. The SID 224 and the timing identifier 226 collectively correspondto the media identifying information that is needed to uniquely identifythe associated media. The wall-clock value 232 represents the value fora detecting timestamp generated by the media monitor 112 at the time ofdetection of the corresponding watermark. For the sake of simplicity,the timing identifiers 226 and the wall-clock values 232 for eachwatermark 201-213 are represented with integer values with each unitincrease corresponding to an additional second in time.

For purposes of illustration, as shown in FIG. 2, the watermarks 201-213are embedded into one of two audio streams designated as either S1 or S2in the illustrated example using one of two watermarking techniques (WT)designated as either A or B. In the illustrated example, the first andsecond watermarks 201, 202 are embedded into the same audio stream (S1)using the same watermarking technique (A). Further, the first and secondwatermarks 201, 202 include consistent media identifying informationbecause they have the same SID (1234) with timing identifiers that arechronologically congruent. As a result of the consistent parametersbetween the first and second watermarks 201, 202, the watermarks areassigned to the same monitoring track 214. In the illustrated example, amedia detection event is defined when at least two consistent watermarksare assigned to the same monitoring track. Accordingly, the first andsecond watermarks are defined as corresponding to a media detectionevent represented by the box indicated by reference numeral 234.

For the reasons set forth below, none of the other watermarks 203-213combine to define additional media detection events because of one ormore inconsistencies between the parameters identified for the differentwatermarks. For example, the third watermark 203 has the same SID (1234)and a chronologically congruent timing identifier to the previous twowatermarks 201, 202 such that the media identifying information betweenall three watermarks is consistent. However, unlike the first twowatermarks 201, 202, the third watermark 203 is embedded using adifferent watermarking technique (B instead of A). As a result, it isassigned to a different track (e.g., the ninth track 222) than the trackcontaining the first two watermarks (e.g., the first track 214). Thus,the third watermark 203 would not be grouped with the previous twowatermarks in connection with the media detection event 234.

The fourth watermark 204 is assigned to another new track (e.g., thefifth track 218) because it is chronologically incongruent with theprevious watermarks. In particular, the fourth watermark 204 wasdetected over 100 seconds after the previous three watermarks 201-203 asindicated by the corresponding wall-clock values 232 (indicative of thetime of the corresponding detecting timestamps) but the timingidentifier 226 of the fourth watermark 204 indicates the watermark wasencoded before at least the second and third watermarks 202, 203.Furthermore, even assuming the timing identifier of the fourth watermark204 was chronologically congruent, the fourth watermark is still placedin a different track because it is embedded in a different audio stream(S2 instead of S1). In some examples, the foregoing analysis for thefourth watermark 204 may be irrelevant because the time interval betweenthe detection of the third watermark 203 and the fourth watermark 204 isgreater than the threshold bridge time. For example, the thresholdbridge time may be 27 seconds but the time between the detection of thetwo watermarks is 142 seconds (based on the difference of the wall-clockvalues 232). Thus, in some such examples, the first and ninth monitoringtracks 214, 222 would be cleared of their corresponding watermarks andmade available for new watermarks before the fourth watermark 204 wasdetected. However, for purposes of explanation, the watermarks 201-213are represented in the different monitoring tracks 214-222 withoutregard to the threshold bridge time elapsing between the watermarks.

The fifth watermark 205 is assigned to another new track (e.g., thesixth track 219) because a different watermarking technique (A insteadof B) was used to embed the watermark as compared with the fourthwatermark 204. Furthermore, the fifth watermark 205 is not grouped withany of the first three watermarks 201-203 because of the different audiostream in which the fifth watermark was embedded. Thus, the fifthwatermark 205 does not form part of a media detection event because itcannot be grouped with any other consistent watermark.

As shown in the illustrated example, the sixth and seventh watermarks206, 207 are assigned to the same monitoring track (e.g., the thirdmonitoring track 216) because their media identifying information isconsistent and the watermarks were embedded in the same audio streamusing the same watermarking technique. In this example, thechronological congruency between the timing identifiers is limited totheir chronological order. While this is sufficient to assign bothwatermarks to the same monitoring track, the watermarks 206, 207 do notresult in a media detection event because the temporal spacing of thetiming identifiers is not chronologically congruent relative to thedetecting timestamps generated by the media monitor 112 based on thecorresponding wall-clock values. In particular, the value for the timingidentifier for the seventh watermark 207 is indicated as being 110seconds after the sixth watermark 206. By contrast, the actualdifference in the time of detection between the two watermarks 206, 207is only three seconds apart. Therefore, the watermarks 206, 207 arediscarded without being designated as a media detection event. In otherexamples, the incongruity of the temporal spacing of the timingidentifiers relative to the wall-clock values (e.g., the detectingtimestamps) may serve as the basis to assign these two watermarks todifferent monitoring tracks. In either case, the sixth and seventhwatermarks 206, 207 do not result in a media detection event.

The eighth and ninth watermarks 208, 209 have consistent mediaidentifying information with the same SID (5678) and chronologicallycongruent timing identifiers. However, the media identifying informationof the eighth and ninth watermarks 208, 209 is not consistent with theprevious seven watermarks 201-207 because the SID is different (5678instead of 1234). Therefore, the eighth and ninth watermarks 208, 209are assigned to different monitoring tracks than the previous watermarks201-207. Furthermore, the eighth and ninth watermarks 208, 209 areassigned to different monitoring tracks relative to one another becausethey are embedded into different audio streams. As a result, the eighthand ninth watermarks 208, 209 do not result in a media detection event.

The tenth and eleventh watermarks 210, 211 share the same SID as thefirst seven watermarks 201-207 and are chronologically congruenttherewith. Accordingly, in the illustrated example, the tenth watermark210 is assigned to the third monitoring track 216 that includes thesixth and seventh watermarks 206, 207 because all three watermarks arealso embedded in the same audio stream (S1) using the same watermarkingtechnique (A). By contrast, the eleventh watermark 210 is assigned tothe ninth monitoring track 222 that includes the third watermark 204because these watermarks are based on a different watermarking technique(B) than the six, seventh, and tenth watermarks 206, 207, 210. Asmentioned above, in many implementations, the similarity of the tenthwatermark 210 to the sixth and seventh watermarks 206, 207 and thesimilarity of the eleventh watermark 211 to the third watermark 203 isirrelevant because the time interval between the watermarks exceeds thethreshold bridge time defined for adjacent ones of the watermarks. Forexample, if the threshold bridge time is 27 seconds, the thirdmonitoring track 216 would be cleared out when the wall-clock valuereached 330 and the ninth monitoring track 222 would be cleared out whenthe wall-clock value reached 131. As shown in the illustrated example,these timeout values occur well before the wall-clock values of 403 and405 associated with the tenth and eleventh watermarks 210, 211. In suchexamples, the tenth and eleventh watermarks 210, 211 would be identifiedas new watermarks that do not correspond to any existing watermarksstored by the media monitor 112 because the associated detectingtimestamps are spaced too far apart. As such, the watermarks would beassigned to new monitoring tracks that may or may not be the same as thetracks used for the third, sixth, and seventh watermarks 203, 206, 207.Nevertheless, for purposes of explanation, these watermarks are shown onthe same monitoring tracks as outlined above. However, as noted in theillustrated example, the watermarks on the same track do not define amedia detection event because they are spaced too far apart (i.e., thetime interval between them is greater than the threshold bridge time).

The twelfth and thirteenth watermarks 212, 213 in the illustratedexample include a different SID than all the previous watermarks butconsistent with each other. In addition to having the same SID, thetwelfth and thirteenth watermarks 212, 213 have an identical timingidentifier (2222) that was detected at the same time (e.g., thewall-clock value for both watermarks is 544 such that the watermarksalso have identical detecting timestamps). These correspond to twowatermarks rather than one watermark because they are embedded indifferent audio streams. However, because the watermarks 212, 213 are indifferent audio streams, they are assigned to different monitoringtracks and, therefore, do not result in a media detection event.

As outlined above, only a single media detection event 234 is generatedfrom all thirteen watermarks 201-213 of FIG. 1. In particular, the firsttwo watermarks 201, 202 are grouped to define the media detection event234 while all the other watermarks 203-213 are either spaced too farapart to be combined (that is, the monitoring track would be cleared ofthe earlier watermarks before the later watermarks are assigned) orisolated on different monitoring tracks due to inconsistencies betweenthe watermarks (based on the media identifying information, the audiostream, and/or the watermarking technique). As a result, each of thelast eleven watermarks 203-213 would be discarded as unreliableindicators of the media they are intended to identify. This is aninefficient system that generates a lot of wasted data.

Examples disclosed herein improve upon the efficiency of the technicalfield of media monitoring and reduce the amount of wasted data bymatching or grouping watermarks detected across different audio streamsand/or across different watermarking technologies. In some examples,this is accomplished by the media monitor 112 assigning each watermarkto multiple different monitoring tracks as illustrated in FIG. 3. Inparticular, FIG. 3 shows the same thirteen watermarks 201-213 assignedto the same monitoring tracks 214-222 as shown in FIG. 2. Additionally,in the illustrated example of FIG. 3, the watermarks 201-213 are alsoassigned to eight additional monitoring tracks 302, 303, 304, 305, 306,307, 308, 309. More specifically, in the illustrated example, eachwatermark 201-213 is assigned to three different tracks including (1) astream-and-technique-specific monitoring track 310, (2) astream-specific monitoring track 312, and (3) a generic monitoring track314.

As used herein, a stream-and-technique-specific monitoring track refersto a track that contains watermarks with consistent media identifyinginformation that are embedded in a specific audio stream using aspecific watermarking technique. That is, for two watermarks to beassigned to the same stream-and-technique-specific monitoring track 310,the watermarks need to have the same SID, chronologically congruenttiming identifiers, and be embedded in the same audio stream using thesame watermarking technology. Thus, as shown in the illustrated exampleof FIG. 3, the first nine monitoring tracks 214-222 (represented bysolid lines) are identified as stream-and-technique-specific monitoringtracks 310. That is, all of the tracks 214-222 shown in FIG. 2 arestream-and-technique-specific monitoring tracks 310.

As used herein, a stream-specific monitoring track refers to a trackthat contains watermarks with consistent media identifying informationthat are embedded in a specific audio stream but may be based on anysuitable watermarking technique. That is, for two watermarks to beassigned to the same stream-specific monitoring track, the watermarksneed to have the same SID, chronologically congruent timing identifiers,and be embedded in the same audio stream. While such watermarks may beembedded using different watermarking techniques, suitable techniquesinclude those that are at least compatible to enable a comparison of theinformation contained in the watermarks. For example, the differenttechniques may implement a common time base so that the timingidentifiers of the different watermarks can be compared for congruency.In the illustrated example of FIG. 3, the tenth through fourteenthmonitoring tracks 302-306 (represented by long-dashed lines) areidentified as stream-specific monitoring tracks 312.

As used herein, a generic monitoring track refers to a track thatcontains watermarks with consistent media identifying informationregardless of the audio stream in which they are embedded and regardlessof the watermarking technique used to embed the watermarks. That is, fortwo watermarks to be assigned to the same stream-specific monitoringtrack, the watermarks need to have the same SID and chronologicallycongruent timing identifiers. While such watermarks may be embedded inany suitable audio stream using different watermarking techniques, asfor the stream-specific monitoring tracks 312, the different techniquesmay need to be sufficiently compatible so that the media identifyinginformation can be appropriately compared. In the illustrated example ofFIG. 3, the fifteenth through seventeenth monitoring tracks 307-309(represented by short-dashed lines) are identified as generic monitoringtracks 312.

The media monitor 112 may additionally or alternatively assignwatermarks to technique-specific monitoring tracks. As used herein, atechnique-specific monitoring track refers to a track that containswatermarks with consistent media identifying information that areembedded using the same watermarking technique but not necessarily inthe same audio stream. That is, for two watermarks to be assigned to thesame technique-specific monitoring track, the watermarks need to havethe same SID, chronologically congruent timing identifiers, and beencoded based on the same watermarking technique.

In some examples, when technique-specific monitoring tracks are used,each watermark may be assigned to four separate monitoring tracks ratherthan three as shown in FIG. 3. In other examples, the watermarks may beassigned to a technique-specific monitoring track in lieu of one of theother three tracks noted above. More generally, the watermarks may beassigned to any combination of one or more of the different types ofmonitoring tracks noted above in accordance with teachings disclosedherein. For instance, the stream-and-technique-specific tracks may beomitted in some examples.

By assigning the watermarks 201-213 to the different types of tracksnoted above, it is possible to identify additional groupings of thewatermarks to generate associated media detection events. For example,as noted above in connection with FIG. 2, the first and secondwatermarks 201, 202 have the same SID, are chronologically congruent,and are embedded in the same audio stream using the same watermarkingtechnique. Thus, they are assigned to the stream-and-technique-specificmonitoring 310 corresponding to the first monitoring track 214. Theassignment of these watermarks 201, 202 in the first track 214 result inthe media detection event 234 as noted above.

In addition to their assignment to the first monitoring track 214, thefirst and second watermarks 201, 202 are both assigned to the tenthmonitoring track 302 because they are associated with the same audiostream and have consistent media identifying information. That is, thetenth monitoring track 302 is a stream-specific track associated withthe first audio stream (S1). In the illustrated example, the third,sixth, seventh, tenth, and eleventh watermarks 203, 206, 207, 210, 211are also assigned to the tenth monitoring track 302 because they arealso embedded in the same audio stream and have consistent mediaidentifying information. As can been seen from FIG. 3, the fact that thethird and eleventh watermarks 203, 211 were embedded using a differentwatermarking technology than the other watermarks 201,202, 206, 207, 210is irrelevant for the tenth monitoring track 302. As mentioned above,the watermarks that are temporally spaced relatively far apart on thetenth monitoring track 302 (or any other track) is for purposes ofillustration. In some examples, each track is cleared of all watermarkswhen the threshold bridge time has elapsed without a new watermark beingassigned to the corresponding track.

In contrast to the watermarks 201-203, 206, 207, 210, 211 shown in thetenth monitoring track 302 of FIG. 3 associated with one audio stream(S1), the fourth and fifth watermarks 204, 205 are associated with adifferent audio stream (S2). As a result, the fourth and fifthwatermarks 204, 205 are assigned to a different stream-specificmonitoring track (the eleventh monitoring track 303) corresponding towatermarks with the particular media identifying information embedded inthe second audio stream (S2). Notably, both watermarks 204, 205 areassigned to the eleventh monitoring track 303 even though they wereembedded using different watermarking techniques because the eleventhtrack is a stream-specific monitoring track that may include watermarksgenerated based on different technologies.

Additionally, in some examples, all of the watermarks 201-207, 210, 211in the tenth and eleventh monitoring tracks 302, 303 are separatelyassigned to a single generic monitoring track (e.g., the fifteenthmonitoring track 307 in FIG. 3). All of these watermarks are assigned tothe same generic monitoring track because they satisfy the requirementof having consistent media identifying information. That the watermarksare embedded in different audio streams using different watermarkingtechnique is irrelevant to the assignment to the generic fifteenthmonitoring track 307.

The eighth and ninth watermarks 208, 209 include different mediaidentifying information (e.g., a different SID) than the watermarksdiscussed above. Therefore, the eight and ninth watermarks 208, 209 areassigned to different monitoring tracks. Furthermore, because the eighthand ninth watermarks 208, 209 are embedded in different audio streams(S1 versus S2), they are assigned to separate stream-specific monitoringtracks 312 (e.g., the twelfth and thirteenth monitoring tracks 304,305). However, the eighth and ninth watermarks 208, 209 are assigned tothe same generic monitoring track 314 (e.g., the sixteenth monitoringtrack 308) because the audio stream is irrelevant for the genericmonitoring track 314.

As mentioned above, the twelfth and thirteenth watermarks 212, 213 aredetected at the same time and have the same timing identifier. However,the points representative of the assignment to the different monitoringtracks are slightly offset in FIG. 3 for purposes of illustration. Inaddition to the assignment of the watermarks 212, 213 to theirrespective stream-and-technique-specific monitoring tracks 215, 221described above in connection with FIG. 2, both watermarks 212 areassigned to the same stream-specific monitoring track 306 because theywere embedded in the same audio stream. Further, both watermarks 212,213 are assigned to the same generic monitoring track 309, which wouldbe the case even if their audio streams or the associated watermarkingtechniques were different.

With the assignment of the watermarks 201-213 in the additionalmonitoring tracks 302-309, many different groupings of the watermarksare possible to form media detection events. As already mentioned, thefirst and second watermarks 201, 202 define the media detection event234 in the first monitoring track 214. However, the first and secondwatermarks 201, 202 define a second media detection event 316 in thetenth monitoring track 302 and a third media detection event 318 in thefifteenth monitoring track 307. Furthermore, as shown in the illustratedexample, the third watermark 203 also forms part of the second and thirdmedia detection events 316, 318. Thus, unlike in FIG. 2 where the thirdwatermark 203 was separate from the first two watermarks 201, 202 andnot used for media identification purposes (i.e., not used to generate amedia detection event), the third watermark 203 in FIG. 3 contributes totwo separate media detection events. This provides additional datapoints that can be used to reliably identify the media being monitored.Furthermore, media detection events become more robust or reliable asthe number of watermarks associated therewith increases. Thus, theinclusion of the third watermark 203 not only increases the number ofmedia detection events but also provides more robust media detectionevents.

As described above in connection with FIG. 2, the fourth and fifthwatermarks 204, 205 are isolated in differentstream-and-technique-specific monitoring tracks 310, thereby preventingthe formulation of an associated media detection event. However, thefourth and fifth watermarks 204, 205 are both assigned to the eleventhand fifteenth monitoring tracks 303, 307, thereby enabling the mediamonitor 112 to identify two additional media detection events 320, 322.A similar result occurs for the tenth and eleventh watermarks 211, 212,with two additional media detection events 324, 326 designated in thetenth and fifteenth monitoring tracks 302, 307. In the illustratedexample, the media detection events 318, 322, 326 in the fifteenthmonitoring track 307 correspond to three separate events rather than asingle event because of the temporal spacing between the separate eventsis greater than the threshold bridge time. In some examples, themonitoring track 307 would be cleared of the watermarks and associatedmedia detection event after the threshold bridge time elapses such thatthe watermarks for the different media detection events 318, 322, 326would not actually be assigned to the same monitoring track (at leastnot at the same time). However, as explained above, the separatewatermarks and separate media detection events are shown in the samemonitoring tracks for purposes of explanation.

No media detection events are generated in connection with the sixth andseventh watermarks 206, 207 for the same reason outlined above inconnection with FIG. 2. Namely, the temporal spacing of the timingidentifiers of the watermarks is inconsistent with the temporal spacingof the corresponding wall-clock values such that the watermarks are nottrustworthy. Accordingly, the sixth and seventh watermarks 206, 207 arediscarded regardless of the monitoring tracks to which they areassigned.

The eighth and ninth watermarks 208, 209 are embedded in different audiostreams and, therefore, are assigned to different stream-specificmonitoring tracks 304, 305. As a result, the watermarks included inthese tracks do not result in media detection events. However, theeighth and ninth watermarks 208, 209 are also assigned to the samegeneric monitoring track 308 such that the watermarks still define oneadditional media detection event 328.

The last two watermarks 212, 213 are a special scenario in which thewatermarks have the same media identifying information (both the sameSID and the same timing identifier) and are based on the samewatermarking technique. These watermarks effectively corresponding to asingle watermark that is detected twice because it was embedded in twodifferent audio streams. In some examples, such watermarks are excludedfrom defining a media detection event by themselves because twoinstances of a single watermark are no more reliable than detecting asingle instance of the watermark. That is, there is the possibility thatthe detected watermarks are actually a false positive based on aparticular noise signal in the media being monitored. Because the samewatermarking technology is used for both audio streams, it is likelythat the same false positive would be detected in both audio streams.Thus, in some examples, the twelfth and thirteenth watermarks 212, 213are discarded (unless grouped with other consistent watermarks assignedto the same monitoring track(s)). In other examples, the twelfth andthirteenth watermarks 212, 213 may be used in combination by themselvesto designate additional media detection events.

While two watermarks detected at the same time using the samewatermarking technique across different audio streams may be suspect,the same concern does not apply to two watermarks detected at the sametime across two different watermarking technologies because there is avery low probability that two different watermarking techniques wouldboth simultaneously produce a false positive. Thus, if the twelfth andthirteenth watermarks 212, 213 were based on different technologies,they could reliably be used to validate one another. In such asituation, the separate watermarks would be grouped to define one ormore additional media detection events.

As shown by comparison between FIGS. 2 and 3, the same watermarks201-213 that resulted in only one media detection event 234 in FIG. 2,are combined in the additional monitoring tracks 302-309 of FIG. 3 toproduce seven additional media detection events 316, 318, 320, 322, 324,326, 328 (and potentially more if the last two watermarks are used todefine events). These additional media events significantly reduce theamount of watermark data that is wasted by being discarded withoutdefining a media detection relative to the approach shown in FIG. 2.Furthermore, the significant increase in the number of media events (aswell as the potential for an increased number of watermarks associatedwith any particular media event) can increase the reliability with whichmedia is detected. Further still, the increase in the number of mediaevents increases the ability of the media monitor 112 to identify mediaitems having a short duration (e.g., under ten seconds). For example,assume that a particular advertisement is only 5 seconds long, which islong enough to embed at most two watermarks spaced two seconds apartusing a particular technology. To identify the media (detect a mediadetection event) would require the detection of both watermarks.However, if additional watermarks were embedded using differentwatermarking techniques and/or embedded in additional audio streams, itwould be possible to miss the detection of one or more of the initialwatermarks and still identify the media by detecting at least twowatermarks across the different technologies and/or the different audiostreams. Furthermore, even if the watermarks are not embedded every twoseconds so that only one watermark was in the 5 second advertisement itwould still be possible to reliably identify the advertisement so longas a second watermark was embedded in a separate audio stream and/orusing a different watermarking technique.

FIG. 4 is a block diagram illustrating an example implementation of theexample media monitor 112 of FIG. 1. The example media monitor 112 ofFIG. 4 includes an example watermark detector 402, an example watermarkanalyzer 404, an example monitoring track controller 406, an examplemonitoring track database 408, an example media detection eventcontroller 410, an example media detection event database 412, anexample event data converter 414, an example transmitter 416, and anexample clock 418.

In the illustrated example, the watermark detector 402 monitors mediareceived by the receiver 110 to detect and extract watermarks embeddedtherein. In some examples, the watermark detector 402 monitors multipledifferent audio streams associated with the media for watermarks.Further, as mentioned above, different watermarks may be embedded basedon different watermarking techniques. Accordingly, in some examples, thewatermark detector 402 implements multiple watermarking techniques todetect and extract watermarks encoded using the different watermarkingtechniques. In other examples, the media monitor 112 may includemultiple watermark detectors associated with different watermarkingtechniques. When a new watermark is detected and extracted, thewatermark detector 402 generates a detecting timestamp indicating thetime when the watermark was detected or captured. In some examples, thedetecting timestamp is generated based on a wall-clock value obtainedfrom the example clock 418.

The example watermark analyzer 404 analyzes the information contained inthe watermark (e.g., media identifying information) and compares it withpreviously detected watermarks. In some examples, the watermark analyzer404 compares the media identifying information of separate watermarks todetermine whether the media identifying information between thewatermarks is consistent. As described above, media identifyinginformation for two watermarks is consistent when there are matchingSIDs and the timing identifiers included in the watermarks arechronologically congruent. In some examples, the watermark analyzer 404determines the chronological congruency of the timing identifiers bycomparing the timing identifiers with one another and with the detectingtimestamp generated by the watermark detector 402 at the time eachwatermark was detected.

Additionally, the watermark analyzer 404 may compare the watermarkingtechnique associated with a newly detected watermark relative topreviously detected watermarks. Further, the watermark analyzer 404 maycompare the audio stream from which a newly detected watermark wasdetected relative to the audio streams corresponding to previouslydetected watermarks.

Comparison of different watermarks by the watermark analyzer 404 enablethe example monitoring track controller 406 to group and/or assign eachnewly detected watermark to one or more monitoring tracks in themonitoring track database 408. In some examples, the monitoring tracksare different memory spaces in the monitoring track database 408 thatenable collected watermarks to be stored in groups based on one or moreof their media identifying information, the audio stream from which theywere extracted, and/or the watermarking technique used to encode andextract the watermarks. If a newly detected watermark is inconsistentwith all previously detected watermarks currently stored in a monitoringtrack in the monitoring track database 408, the monitoring trackdatabase 408 may assign the watermark to a new monitoring track.Periodically, the monitoring track controller 406 discards watermarksstored in different monitoring tracks to clear out the tracks and makethem available for subsequently detected watermarks. In some examples,the monitoring track controller 406 discards watermarks in a particularmonitoring track based on a threshold bridge time having elapsed duringwhich no new watermarks were assigned to the particular monitoringtrack. Thus, in some examples, the monitoring track controller 406initiates a timer using the clock 418 when a new monitoring track isgenerated and assigned a first watermark and resets the timer each timea new watermark is assigned to the track until the timer exceeds thethreshold bridge time.

The example media detection event controller 410 of FIG. 4 analyzes thewatermarks stored in the monitoring tracks of the monitoring trackdatabase 408 to identify media detection events. A media detection eventoccurs when a threshold number of watermarks are assigned to the samemonitoring track. In some examples, the threshold number is 2 but may beany other suitable number (e.g., 3, 4, 5, etc.). Once the thresholdnumber of watermarks in a single monitoring track have been satisfied,the media detection event controller 410 generates a media detectionevent that is stored in the media detection event database 412. In someexamples, a media detection event includes the SID extracted from thewatermarks defining the media detection event and timing informationbased on the timing identifiers of the watermarks. The media detectionevent may also include information indicative of the detecting timestampgenerated at the time the watermarks were detected. Further, in someexamples, the media detection event includes an indication of the numberof watermarks associated with the event as well as the audio stream(s)and/or the watermarking technique(s) associated with the watermarks.

As mentioned above, as additional watermarks are detected, they may beassigned to the same monitoring track that is already associated with amedia detection event. As such, as new watermarks are assigned toexisting monitoring tracks, the example media detection event controller410 may associate the new watermarks with the corresponding mediadetection event(s) and update the associated information accordingly.

In some examples, once the threshold bridge time has elapsed inconnection with a monitoring track associated with a media detectionevent, the example event data converter 414 converts the media detectionevent into a converted format for transmission to the data collectionfacility 114. For example, the event data converter 414 may encrypt,decrypt, compress, modify, etc., the media detection event to, forexample, reduce the amount of data to be transmitted to the datacollection facility 114. In some examples, the event data converter 414combines multiple media detection events together into aggregated eventdata for transmission to the data collection facility 114. In theillustrated example, the transmitter 416 transmits the converted eventdata to the data collection facility 114 via, for example, the Internetand/or any other suitable communication means. While the converted eventdata is transmitted in substantially real-time in the illustratedexample, in some examples, the converted event data is stored, cached,and/or buffered before being transmitted to the data collection facility114.

While an example manner of implementing the media monitor 112 of FIG. 1is illustrated in FIG. 4, one or more of the elements, processes and/ordevices illustrated in FIG. 4 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample watermark detector 402, the example watermark analyzer 404, theexample monitoring track controller 406, the example monitoring trackdatabase 408, the example media detection event controller 410, theexample media detection event database 412, the example event dataconverter 414, the example transmitter 416, the example clock 418,and/or, more generally, the example media monitor 112 of FIG. 4 may beimplemented by hardware, software, firmware and/or any combination ofhardware, software and/or firmware. Thus, for example, any of theexample watermark detector 402, the example watermark analyzer 404, theexample monitoring track controller 406, the example monitoring trackdatabase 408, the example media detection event controller 410, theexample media detection event database 412, the example event dataconverter 414, the example transmitter 416, the example clock 418,and/or, more generally, the example media monitor 112 could beimplemented by one or more analog or digital circuit(s), logic circuits,programmable processor(s), programmable controller(s), graphicsprocessing unit(s) (GPU(s)), digital signal processor(s) (DSP(s)),application specific integrated circuit(s) (ASIC(s)), programmable logicdevice(s) (PLD(s)) and/or field programmable logic device(s) (FPLD(s)).When reading any of the apparatus or system claims of this patent tocover a purely software and/or firmware implementation, at least one ofthe example watermark detector 402, the example watermark analyzer 404,the example monitoring track controller 406, the example monitoringtrack database 408, the example media detection event controller 410,the example media detection event database 412, the example event dataconverter 414, the example transmitter 416, and/or the example clock 418is/are hereby expressly defined to include a non-transitory computerreadable storage device or storage disk such as a memory, a digitalversatile disk (DVD), a compact disk (CD), a Blu-ray disk, etc.including the software and/or firmware. Further still, the example mediamonitor 112 of FIG. 1 may include one or more elements, processes and/ordevices in addition to, or instead of, those illustrated in FIG. 4,and/or may include more than one of any or all of the illustratedelements, processes and devices. As used herein, the phrase “incommunication,” including variations thereof, encompasses directcommunication and/or indirect communication through one or moreintermediary components, and does not require direct physical (e.g.,wired) communication and/or constant communication, but ratheradditionally includes selective communication at periodic intervals,scheduled intervals, aperiodic intervals, and/or one-time events.

A flowchart representative of example hardware logic, machine readableinstructions, hardware implemented state machines, and/or anycombination thereof for implementing the media monitor 112 of FIGS. 1and/4 is shown in FIGS. 5 and 6. The machine readable instructions maybe an executable program or portion of an executable program forexecution by a computer processor such as the processor 712 shown in theexample processor platform 700 discussed below in connection with FIG.7. The program may be embodied in software stored on a non-transitorycomputer readable storage medium such as a CD-ROM, a floppy disk, a harddrive, a DVD, a Blu-ray disk, or a memory associated with the processor712, but the entire program and/or parts thereof could alternatively beexecuted by a device other than the processor 712 and/or embodied infirmware or dedicated hardware. Further, although the example program isdescribed with reference to the flowchart illustrated in FIGS. 5 and 6,many other methods of implementing the example media monitor 112 mayalternatively be used. For example, the order of execution of the blocksmay be changed, and/or some of the blocks described may be changed,eliminated, or combined. Additionally or alternatively, any or all ofthe blocks may be implemented by one or more hardware circuits (e.g.,discrete and/or integrated analog and/or digital circuitry, an FPGA, anASIC, a comparator, an operational-amplifier (op-amp), a logic circuit,etc.) structured to perform the corresponding operation withoutexecuting software or firmware.

As mentioned above, the example processes of FIGS. 5 and 6 may beimplemented using executable instructions (e.g., computer and/or machinereadable instructions) stored on a non-transitory computer and/ormachine readable medium such as a hard disk drive, a flash memory, aread-only memory, a compact disk, a digital versatile disk, a cache, arandom-access memory and/or any other storage device or storage disk inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, for brief instances, for temporarily buffering,and/or for caching of the information). As used herein, the termnon-transitory computer readable medium is expressly defined to includeany type of computer readable storage device and/or storage disk and toexclude propagating signals and to exclude transmission media.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim employs any formof “include” or “comprise” (e.g., comprises, includes, comprising,including, having, etc.) as a preamble or within a claim recitation ofany kind, it is to be understood that additional elements, terms, etc.may be present without falling outside the scope of the correspondingclaim or recitation. As used herein, when the phrase “at least” is usedas the transition term in, for example, a preamble of a claim, it isopen-ended in the same manner as the term “comprising” and “including”are open ended. The term “and/or” when used, for example, in a form suchas A, B, and/or C refers to any combination or subset of A, B, C such as(1) A alone, (2) B alone, (3) C alone, (4) A with B, (5) A with C, (6) Bwith C, and (7) A with B and with C.

The program of FIG. 5 begins at block 502 where the example watermarkdetector 402 monitors media for watermarks. As described above, thewatermark detector 402 may monitor multiple audio streams associatedwith the media. Further, the watermark detector 402 may monitor themedia for watermarks embedded using different watermarking techniques.At block 504, the example watermark detector 402 extracts a newwatermark from an audio stream of the media embedded using a particularwatermarking technique. At block 506, the example watermark detector 402generates a detecting timestamp for the new watermark.

At block 508, the example watermark analyzer 404 assigns the newwatermark to appropriate monitoring tracks as explained in furtherdetail in connection with the example program of FIG. 6. Turning to FIG.6, the example process begins at block 602 where the example watermarkanalyzer 404 determines whether the media identifying information (e.g.,the SID and the timing identifier) in the new watermark are consistentwith a previously detected watermark. In some examples, the watermarkanalyzer 404 compares the media identifying information to all otherwatermarks currently stored in at least one monitoring track in themonitoring track database 408. In some examples, the watermark analyzer404 compares the media identifying information with the most recent orlast watermark added to each monitoring track without regard to anypreviously detected watermarks assigned to the same monitoring trackbecause all watermarks in the same track have consistent mediaidentifying information. If the watermark analyzer 404 determines thatthe media identifying information in the new watermark is not consistentwith any previously detected watermark, control advances to block 604.

At block 604, the example monitoring track controller 406 assigns thenew watermark to a new generic monitoring track (e.g., one of thegeneric monitoring tracks 314 of FIG. 3). Thereafter, at block 606, theexample monitoring track controller 406 initiates a timer for the newgeneric track. Further, in some examples, at block 608, the examplemonitoring track controller 406 assigns the new watermark to a newstream-specific monitoring track (e.g., one of the stream-specificmonitoring tracks 312 of FIG. 3). Thereafter, at block 610, the examplemonitoring track controller 406 initiates a timer for the newstream-specific monitoring track. Further, in some examples, at block612, the example monitoring track controller 406 assigns the newwatermark to a new stream-and-technique-specific monitoring track (e.g.,one of the stream-and-technique-specific monitoring tracks 310 of FIG.3). Thereafter, at block 614, the example monitoring track controller406 initiates a timer for the new stream-specific monitoring track.While not represented in FIG. 6, the example monitoring track controller406 may additionally or alternatively assign the new watermark to a newtechnique-specific monitoring track. Thus, in some examples, the newwatermark may be assigned to as many as four different monitoringtracks. In other examples, one or more of the four different monitoringtracks may be omitted. For instance, in some examples, the new watermarkmay be assigned only to a stream-specific monitoring track. Once the newwatermark has been assigned to all relevant monitoring tracks, theexample process of FIG. 6 ends and returns to complete the process ofFIG. 5.

Returning to block 602 in FIG. 6, if the watermark analyzer 404determines that the media identifying information in the new watermarkis consistent with a previously detected watermark, control advances toblock 616. At block 616, the example monitoring track controller 406assigns the new watermark to the generic monitoring track (e.g., one ofthe generic monitoring tracks 314 of FIG. 3) associated with theconsistent previous watermark. Inasmuch as the generic monitoring trackalready has at least one watermark assigned to it (e.g., the consistentprevious watermark), the monitoring track controller 406 would havealready initiated a timer. This would have occurred when the genericmonitoring track was generated and assigned its first watermark(corresponding to block 604 and 606 described above). Accordingly, atblock 618, the example monitoring track controller 406 resets the timerfor the generic monitoring track.

At block 620, the example media detection event controller 410determines whether the generic monitoring track contains a thresholdnumber of watermarks to define a media detection event. In someexamples, the threshold number is two. If the threshold has beensatisfied, control advances to block 622 where the example mediadetection event controller 410 groups the new watermark with a mediadetection event associated with the consistent previous watermark andthe corresponding generic monitoring track. In examples where the newwatermark is the first time the threshold number of watermarks has beenmet, the example media detection event controller 410 generates a newmedia detection event that is stored in the media detection eventdatabase 412. If the threshold number of watermarks has already beensatisfied, the media detection event controller 410 may update thepreviously created media detection event with the new watermark. Oncethe new watermark is associated with the media detection event, controladvances to block 624. Returning to block 620, if the example mediadetection event controller 410 determines that the generic monitoringtrack does not contain the threshold number of watermarks, controladvances directly to block 624.

At block 624, the example watermark analyzer 404 determines whether thenew watermark is embedded in the same audio stream as a consistentprevious watermark. If not, control advances to block 608 where theexample monitoring track controller 406 assigns the new watermark to anew stream-specific monitoring track. If the new watermark is embeddedin the same audio stream as the consistent previous watermark (block624), control advances to block 626. In some examples, the consistentprevious watermark referenced in block 624 may be the same consistentprevious watermark as referenced in blocks 616-622. However, in otherexamples, the consistent previous watermark referenced in block 624 mayrefer to a different consistent previous watermark.

At block 626, the example monitoring track controller 406 assigns thenew watermark to the stream-specific monitoring track (e.g., one of thestream-specific monitoring tracks 312 of FIG. 3) associated with theconsistent previous watermark. At block 628, the example monitoringtrack controller 406 resets the timer for the stream-specific monitoringtrack. At block 630, the example media detection event controller 410determines whether the stream-specific monitoring track contains athreshold number of watermarks to define a media detection event. If so,control advances to block 632 where the example media detection eventcontroller 410 groups the new watermark with a media detection eventassociated with the consistent previous watermark and the correspondingstream-specific monitoring track. Thereafter, control advances to block634. Returning to block 630, if the example media detection eventcontroller 410 determines that the stream-specific monitoring track doesnot contain the threshold number of watermarks, control advancesdirectly to block 634.

At block 634, the example watermark analyzer 404 determines whether thenew watermark is embedded using the same watermarking technique as aconsistent previous watermark. If not, control advances to block 612where the example monitoring track controller 406 assigns the newwatermark to a new stream-and-technique-specific monitoring track. Ifthe new watermark is embedded using the same watermarking technique asthe consistent watermarking technique (block 634), control advances toblock 636. In some examples, the consistent previous watermarkreferenced in block 634 may be the same consistent previous watermark asreferenced in blocks 616-622 and/or in blocks 624-632. However, in otherexamples, the consistent previous watermark referenced in block 634 mayrefer to a different consistent previous watermark to one or both of theconsistent previous watermarks referenced in blocks 616-622 and blocks624-632.

At block 636, the example monitoring track controller 406 assigns thenew watermark to the stream-and-technique-specific monitoring track(e.g., one of the stream-and-technique-specific monitoring tracks 310 ofFIG. 3) associated with the consistent previous watermark. At block 638,the example monitoring track controller 406 resets the timer for thestream-and-technique-specific monitoring track. At block 640, theexample media detection event controller 410 determines whether thestream-and-technique-specific monitoring track contains a thresholdnumber of watermarks to define a media detection event. If so, controladvances to block 642 where the example media detection event controller410 groups the new watermark with a media detection event associatedwith the consistent previous watermark and the correspondingstream-and-technique-specific monitoring track. Thereafter, the exampleprocess of FIG. 6 ends and returns to complete the process of FIG. 5.Returning to block 640, if the example media detection event controller410 determines that the stream-and-technique-specific monitoring trackdoes not contain the threshold number of watermarks, the example processof FIG. 6 ends and returns to complete the process of FIG. 5.

Returning to FIG. 5, once the new watermark has been assigned toappropriate monitoring tracks (block 508) as detailed in FIG. 6, controladvances to block 510. At block 510, the example monitoring trackcontroller 406 determines whether a timer for a monitoring track hasexceeded a threshold bridge time. In this example, the timer correspondsto the timers initiated or reset at any one of blocks 606, 610, 614,618, 628, 638 of FIG. 6. In some examples, the threshold bridge timedesignates a period of time that may elapse between the detection ofwatermarks grouped together and assigned to the same track. Thethreshold bridge time may be set to any suitable duration (e.g., 15seconds, 27 seconds, 45 seconds, 60 seconds, etc.). If the timer hasexceeded the threshold bridge time, control advances to block 512 wherethe example media detection event controller 410 determines whetherthere is a media detection event associated with the monitoring track.If so, the example transmitter 416 reports the media detection event toa data collection facility (e.g., the data collection facility 114). Insome examples, the media detection event is provided to the event dataconverter to convert the event and/or combine the event with other mediadetection events before being reported to the data collection facility.Thereafter, control advances to block 518.

Returning to block 512, if the media detection event controller 410determines that there is no media detection event associated with themonitoring track, control advances to block 516. At block 516, theexample monitoring track controller 406 discards the watermark(s) in themonitoring track and designates the track as available for reassignment.Thereafter, control advances to block 518. Returning to block 510, ifthe example monitoring track controller 406 determines that the timerfor the monitoring track has not exceeded the threshold bridge time,control advances directly to block 518.

At block 518, the example monitoring track controller 406 determineswhether there is another monitoring track to analyze. If so, controlreturns to block 510. Otherwise, control advances to block 520 where theexample process determines whether to continue monitoring the media. Ifso, control returns to block 502. Otherwise, the example process of FIG.5 ends.

FIG. 7 is a block diagram of an example processor platform 700structured to execute the instructions of FIGS. 5 and 6 to implement themedia monitor 112 of FIGS. 1 and/or 4. The processor platform 700 canbe, for example, a server, a personal computer, a workstation, aself-learning machine (e.g., a neural network), a mobile device (e.g., acell phone, a smart phone, a tablet such as an iPad™), a personaldigital assistant (PDA), an Internet appliance, a set top box, or anyother type of computing device.

The processor platform 700 of the illustrated example includes aprocessor 712. The processor 712 of the illustrated example is hardware.For example, the processor 712 can be implemented by one or moreintegrated circuits, logic circuits, microprocessors, GPUs, DSPs, orcontrollers from any desired family or manufacturer. The hardwareprocessor may be a semiconductor based (e.g., silicon based) device. Inthis example, the processor implements example watermark detector 402,the example watermark analyzer 404, the example monitoring trackcontroller 406, the example media detection event controller 410, theexample event data converter 414, the example transmitter 416, theexample clock 418.

The processor 712 of the illustrated example includes a local memory 713(e.g., a cache). The processor 712 of the illustrated example is incommunication with a main memory including a volatile memory 714 and anon-volatile memory 716 via a bus 718. The volatile memory 714 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS® Dynamic Random Access Memory(RDRAM®) and/or any other type of random access memory device. Thenon-volatile memory 716 may be implemented by flash memory and/or anyother desired type of memory device. Access to the main memory 714, 716is controlled by a memory controller.

The processor platform 700 of the illustrated example also includes aninterface circuit 720. The interface circuit 720 may be implemented byany type of interface standard, such as an Ethernet interface, auniversal serial bus (USB), a Bluetooth® interface, a near fieldcommunication (NFC) interface, and/or a PCI express interface.

In the illustrated example, one or more input devices 722 are connectedto the interface circuit 720. The input device(s) 722 permit(s) a userto enter data and/or commands into the processor 712. The inputdevice(s) can be implemented by, for example, an audio sensor, amicrophone, a camera (still or video), a keyboard, a button, a mouse, atouchscreen, a track-pad, a trackball, isopoint and/or a voicerecognition system.

One or more output devices 724 are also connected to the interfacecircuit 720 of the illustrated example. The output devices 724 can beimplemented, for example, by display devices (e.g., a light emittingdiode (LED), an organic light emitting diode (OLED), a liquid crystaldisplay (LCD), a cathode ray tube display (CRT), an in-place switching(IPS) display, a touchscreen, etc.), a tactile output device, a printerand/or speaker. The interface circuit 720 of the illustrated example,thus, typically includes a graphics driver card, a graphics driver chipand/or a graphics driver processor.

The interface circuit 720 of the illustrated example also includes acommunication device such as a transmitter, a receiver, a transceiver, amodem, a residential gateway, a wireless access point, and/or a networkinterface to facilitate exchange of data with external machines (e.g.,computing devices of any kind) via a network 726. The communication canbe via, for example, an Ethernet connection, a digital subscriber line(DSL) connection, a telephone line connection, a coaxial cable system, asatellite system, a line-of-site wireless system, a cellular telephonesystem, etc.

The processor platform 700 of the illustrated example also includes oneor more mass storage devices 728 for storing software and/or data. Inthis example, the mass storage device includes, the example monitoringtrack database 408 and the example media detection event database 412.Examples of such mass storage devices 728 include floppy disk drives,hard drive disks, compact disk drives, Blu-ray disk drives, redundantarray of independent disks (RAID) systems, and digital versatile disk(DVD) drives.

The machine executable instructions 732 of FIGS. 5 and 6 may be storedin the mass storage device 728, in the volatile memory 714, in thenon-volatile memory 716, and/or on a removable non-transitory computerreadable storage medium such as a CD or DVD.

From the foregoing, it will be appreciated that example methods,apparatus, and articles of manufacture have been disclosed that reducethe amount of wasted or discarded data collected at a media monitoringsite by enabling the validation or authentication of watermarks throughthe grouping of watermarks detected across different audio streamsassociated with media being monitored and/or across differentwatermarking techniques. More particularly, rather than disregarding asingle watermark detected in a particular audio stream and/or embeddedusing a particular technology because no other watermarks are detectedwithin a relevant period of time in the same audio stream and/or basedon the same watermarking technique, in examples disclosed herein, thewatermark may be grouped with other watermarks in different audiostreams and/or detected based on different watermarking techniques. Acorollary to the reduction in the amount of data that is discarded is anincrease in the amount of reliable data (e.g., media detection events)that may be used to identify media being monitored. Furthermore,examples disclosed herein give rise to the possibility of any particularmedia detection event having a greater number of watermarks associatedthereto, thereby increasing the reliability of the collected data.Further, the increased number of media detection events made possible byteachings disclosed herein results in an increased frequency at whichsuch media detection events are likely to be detected. As a result,examples disclosed herein are capable of detecting shorter media items(e.g., advertisements that are less than 10 seconds long) than istechnically feasible using known approaches because of the technologicallimit on the duration or associated frequency at which a singlewatermark may be embedded in an audio stream and still be concealed froma human exposed to the media.

Example 1 includes an apparatus comprising a watermark detector todetect a first watermark embedded in a first audio stream associatedwith media and to detect a second watermark embedded in a second audiostream associated with the media, the second audio stream beingdifferent than the first audio stream, a watermark analyzer to comparefirst media identifying information in the first watermark with secondmedia identifying information in the second watermark, a media detectionevent controller to associate the first and second watermarks with amedia detection event when the first media identifying information isconsistent with the second media identifying information, and atransmitter to transmit the media detection event to a data collectionfacility.

Example 2 includes the apparatus as defined in example 1, wherein thefirst media identifying information includes a first source identifierand a first timing identifier and the second media identifyinginformation includes a second source identifier and a second timingidentifier, wherein the first media identifying information isconsistent with the second media identifying information when the firstsource identifier matches the second source identifier and the first andsecond timing identifiers match an order in which the first and secondwatermarks were detected.

Example 3 includes the apparatus as defined in example 2, wherein thewatermark detector is to assign a first timestamp to the first watermarkwhen the first watermark is detected and to assign a second timestamp tothe second watermark when the second watermark is detected, the mediadetection event controller to associate the first and second watermarkswith a media detection when an interval between the first timestamp andthe second timestamp is less than a threshold, and to disregard thefirst and second watermarks when the interval is greater than thethreshold.

Example 4 includes the apparatus as defined in example 3, wherein themedia detection event controller is to disregard the first and secondwatermarks when the first timestamp matches the second timestamp.

Example 5 includes the apparatus as defined in any one of examples 1-3,wherein the first watermark is embedded in the first audio stream basedon a first watermarking technique and the second watermark is embeddedin the second audio stream based on a second watermarking technique.

Example 6 includes the apparatus as defined in example 5, wherein thewatermark detector is to detect a third watermark embedded in the firstaudio stream based on the second watermarking technique, the thirdwatermark embedded in the first audio stream based on the secondwatermarking technique.

Example 7 includes the apparatus as defined in any one of examples 1-5,further including a monitoring track controller to assign the firstwatermark to a first monitoring track and a second monitoring track, thefirst and second monitoring tracks associated with a series ofwatermarks having consistent media identifying information, the firstmonitoring track including ones of the series of watermarks embedded inthe first audio stream using a first watermarking technique, the secondmonitoring track including ones of the series of watermarks embeddedusing the first watermarking technique regardless of the audio stream.

Example 8 includes the apparatus as defined in example 7, wherein themonitoring track controller is to assign the first watermark to a thirdmonitoring track, the third monitoring track including ones of theseries of watermarks regardless of the audio stream and regardless ofthe watermarking technique used to embed the watermarks.

Example 9 includes the apparatus as defined in any one of examples 1-8,wherein the watermark detector monitors both the first and second audiostreams at the same time.

Example 10 includes the apparatus as defined in any one of examples 1-9,wherein the first and second audio streams correspond to differentrepresentations of audio corresponding to the same visual content of themedia.

Example 11 includes a non-transitory computer readable medium comprisinginstructions that, when executed, cause a machine to at least detect afirst watermark embedded in a first audio stream associated with media,detect a second watermark embedded in a second audio stream associatedwith the media different than the first audio stream, compare firstmedia identifying information in the first watermark with second mediaidentifying information in the second watermark, associate the first andsecond watermarks with a media detection event when the first mediaidentifying information is consistent with the second media identifyinginformation, and transmit the media detection event to a data collectionfacility.

Example 12 includes the non-transitory computer readable medium asdefined in example 11, wherein the first media identifying informationincludes a first source identifier and a first timing identifier and thesecond media identifying information includes a second source identifierand a second timing identifier, the instructions further causing themachine to determine the first media identifying information isconsistent with the second media identifying information when the firstsource identifier matches the second source identifier and the first andsecond timing identifiers match an order in which the first and secondwatermarks were detected.

Example 13 includes the non-transitory computer readable medium asdefined in example 12, wherein the instructions further cause themachine to assign a first timestamp to the first watermark when thefirst watermark is detected, assign a second timestamp to the secondwatermark when the second watermark is detected, associate the first andsecond watermarks with a media detection when an interval between thefirst timestamp and the second timestamp is less than a threshold, anddisregard the first and second watermarks when the interval is greaterthan the threshold.

Example 14 includes the non-transitory computer readable medium asdefined in any one of examples 11-13, wherein the instructions furthercause the machine to detect the first watermark based on a firstwatermarking technique, and detect the second watermark based on asecond watermarking technique different than the first watermarkingtechnique, the first watermark embedded in the first audio stream basedon the first watermarking technique and the second watermark embedded inthe second audio stream based on the second watermarking technique.

Example 15 includes the non-transitory computer readable medium asdefined in example 14, wherein the instructions further cause themachine to detect a third watermark embedded in the first audio streambased on the second watermarking technique, the third watermark embeddedin the first audio stream based on the second watermarking technique.

Example 16 includes the non-transitory computer readable medium asdefined in any one of examples 11-15, wherein the instructions furthercause the machine to assign the first watermark to a first monitoringtrack and a second monitoring track, the first and second monitoringtracks associated with a series of watermarks having consistent mediaidentifying information, the first monitoring track including ones ofthe series of watermarks embedded in the first audio stream using afirst watermarking technique, the second monitoring track including onesof the series of watermarks embedded using the first watermarkingtechnique regardless of the audio stream.

Example 17 includes the non-transitory computer readable medium asdefined in example 16, wherein the instructions further cause themachine to assign the first watermark to a third monitoring track, thethird monitoring track including ones of the series of watermarksregardless of the audio stream and regardless of the watermarkingtechnique used to embed the watermarks.

Example 18 includes a method comprising detecting, by executing aninstruction with a processor, a first watermark embedded in a firstaudio stream associated with media, detecting, by executing aninstruction with the processor, a second watermark embedded in a secondaudio stream associated with the media different than the first audiostream, comparing, by executing an instruction with the processor, firstmedia identifying information in the first watermark with second mediaidentifying information in the second watermark, associating, byexecuting an instruction with the processor, the first and secondwatermarks with a media detection event when the first media identifyinginformation is consistent with the second media identifying information,and transmitting the media detection event to a data collectionfacility.

Example 19 includes the method as defined in example 18, wherein thefirst media identifying information includes a first source identifierand a first timing identifier and the second media identifyinginformation includes a second source identifier and a second timingidentifier, the method further including determining the first mediaidentifying information is consistent with the second media identifyinginformation when the first source identifier matches the second sourceidentifier and the first and second timing identifiers match an order inwhich the first and second watermarks were detected.

Example 20 includes the method as defined in example 19, furtherincluding assigning a first timestamp to the first watermark when thefirst watermark is detected, assigning a second timestamp to the secondwatermark when the second watermark is detected, associating the firstand second watermarks with a media detection when an interval betweenthe first timestamp and the second timestamp is less than a threshold,and disregarding the first and second watermarks when the interval isgreater than the threshold.

Example 21 includes the method as defined in any one of examples 18-20,further including detecting the first watermark based on a firstwatermarking technique, and detecting the second watermark based on asecond watermarking technique different than the first watermarkingtechnique, the first watermark embedded in the first audio stream basedon the first watermarking technique and the second watermark embedded inthe second audio stream based on the second watermarking technique.

Example 22 includes the method as defined in any one of examples 18-21,further including assigning the first watermark to a first monitoringtrack and a second monitoring track, the first and second monitoringtracks associated with a series of watermarks having consistent mediaidentifying information, the first monitoring track including ones ofthe series of watermarks embedded in the first audio stream using afirst watermarking technique, the second monitoring track including onesof the series of watermarks embedded using the first watermarkingtechnique regardless of the audio stream.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus comprising: a watermark detector to:detect a first watermark embedded in a first audio stream associatedwith media, the first watermark including a first source identifier anda first timing identifier; and detect a second watermark embedded in asecond audio stream associated with the media, the second audio streamdifferent than the first audio stream, the second watermark including asecond source identifier and a second timing identifier; a watermarkanalyzer to: determine whether the first and second source identifiersmatch; and determine whether the first and second timing identifiers arechronologically congruent; a controller to associate the first andsecond watermarks with a media detection event when both (1) the firstand second source identifiers match and (2) the first and second timingidentifiers are chronologically congruent, the media detection eventcorresponding to a group of watermarks, the group of watermarksincluding a threshold number of watermarks, the threshold number beingat least two; and a transmitter to transmit the media detection event toa data collection facility.
 2. The apparatus of claim 1, wherein thecontroller is not to associate the first and second watermarks with themedia detection event when (1) the first and second source identifiersdo not match or (2) the first and second timing identifiers are notchronologically congruent.
 3. The apparatus of claim 1, wherein thewatermark detector is to (i) assign a first timestamp to the firstwatermark when the first watermark is detected and (ii) assign a secondtimestamp to the second watermark when the second watermark is detected,and the controller is to: associate the first and second watermarks withthe media detection event when an interval between the first timestampand the second timestamp is less than a threshold; and not associate thefirst and second watermarks with the media detection event when theinterval is greater than the threshold.
 4. The apparatus of claim 3,wherein the controller is not to associate the first and secondwatermarks with the media detection event when the first timestampmatches the second timestamp.
 5. The apparatus of claim 1, wherein thefirst watermark is embedded in the first audio stream based on a firstwatermarking technique, the second watermark is embedded in the secondaudio stream based on a second watermarking technique, and the watermarkdetector is to (i) detect the first watermark based on the firstwatermarking technique and (ii) detect the second watermark based on thesecond watermarking technique.
 6. The apparatus of claim 5, wherein thewatermark detector is to detect a third watermark embedded in the firstaudio stream based on the second watermarking technique, the thirdwatermark embedded in the first audio stream based on the secondwatermarking technique.
 7. The apparatus of claim 1, wherein thecontroller is a first controller, and further including a secondcontroller to: assign a first series of watermarks to a first monitoringtrack, the first series of watermarks limited to watermarks embedded inthe first audio stream based on a first watermarking technique; andassign a second series of watermarks to a second monitoring track, thesecond series of watermarks including watermarks embedded in either thefirst audio stream or the second audio stream based on the firstwatermarking technique, both the first and second series of watermarksincluding the first watermark.
 8. The apparatus of claim 7, wherein thesecond controller is to assign a third series of watermarks to a thirdmonitoring track, the third series of watermarks including watermarksembedded in either the first audio stream or the second audio streambased on either the first watermarking technique or a secondwatermarking technique, the third series of watermarks including boththe first watermark and the second watermark.
 9. The apparatus of claim1, wherein the watermark detector is to monitor the first and secondaudio streams simultaneously.
 10. An apparatus comprising: at least onememory; computer readable instructions in the apparatus; and processorcircuitry to execute the computer readable instructions to at least:detect a first watermark embedded in a first audio stream associatedwith media, the first watermark including a first source identifier anda first timing identifier; detect a second watermark embedded in asecond audio stream associated with the media, the second audio streamdifferent than the first audio stream, the second watermark including asecond source identifier and a second timing identifier; determinewhether the first and second source identifiers match; determine whetherthe first and second timing identifiers are chronologically congruentrelative to first and second times when the respective first and secondwatermarks were detected; associate the first and second watermarks witha media detection event when both (1) the first and second sourceidentifiers match and (2) the first and second timing identifiers arechronologically congruent; and transmit the media detection event to adata collection facility.
 11. The apparatus of claim 10, wherein theprocessor circuitry is not to associate the first and second watermarkswith the media detection event when (1) the first and second sourceidentifiers do not match or (2) the first and second timing identifiersare not chronologically congruent.
 12. The apparatus of claim 10,wherein the processor circuitry is to: assign a first timestamp to thefirst watermark when the first watermark is detected; assign a secondtimestamp to the second watermark when the second watermark is detected;associate the first and second watermarks with the media detection eventwhen an interval between the first timestamp and the second timestamp isless than a threshold; and not associate the first and second watermarkswith the media detection event when the interval is greater than thethreshold.
 13. The apparatus of claim 12, wherein the processorcircuitry is not to associate the first and second watermarks with themedia detection event when the first timestamp matches the secondtimestamp.
 14. The apparatus of claim 10, wherein the first watermark isembedded in the first audio stream based on a first watermarkingtechnique, the second watermark is embedded in the second audio streambased on a second watermarking technique, and the processor circuitry isto (i) detect the first watermark based on the first watermarkingtechnique and (ii) detect the second watermark based on the secondwatermarking technique.
 15. The apparatus of claim 14, wherein theprocessor circuitry is to detect a third watermark embedded in the firstaudio stream based on the second watermarking technique, the thirdwatermark embedded in the first audio stream based on the secondwatermarking technique.
 16. The apparatus of claim 10, wherein theprocessor circuitry is to: assign a first series of watermarks to afirst monitoring track, the first series of watermarks limited towatermarks embedded in the first audio stream based on a firstwatermarking technique; and assign a second series of watermarks to asecond monitoring track, the second series of watermarks includingwatermarks embedded in either the first audio stream or the second audiostream based on the first watermarking technique, both the first andsecond series of watermarks including the first watermark.
 17. Theapparatus of claim 16, wherein the processor circuitry is to assign athird series of watermarks to a third monitoring track, the third seriesof watermarks including watermarks embedded in either the first audiostream or the second audio stream based on either the first watermarkingtechnique or a second watermarking technique, the third series ofwatermarks including both the first watermark and the second watermark.18. The apparatus of claim 10, wherein the processor circuitry is tomonitor the first and second audio streams simultaneously.
 19. Theapparatus of claim 10, wherein the first and second watermarks are to bediscarded without being transmitted to the data collection facility when(1) the first and second source identifiers do not match or (2) thefirst and second timing identifiers are not chronologically congruent.20. A non-transitory computer readable medium comprising instructionsthat, when executed, cause a machine to at least: detect a firstwatermark embedded in a first audio stream associated with media, thefirst watermark including a first source identifier and a first timingidentifier; detect a second watermark embedded in a second audio streamassociated with the media, the second audio stream different than thefirst audio stream, the second watermark including a second sourceidentifier and a second timing identifier; determine whether the firstand second source identifiers match; determine whether the first andsecond timing identifiers are chronologically congruent; group the firstand second watermarks to form a media detection event when both (1) thefirst and second source identifiers match and (2) the first and secondtiming identifiers are chronologically congruent; and transmit the mediadetection event to a data collection facility.
 21. The non-transitorycomputer readable medium of claim 20, wherein the instructions furthercause the machine not to group the first and second watermarks to formthe media detection event when (1) the first and second sourceidentifiers do not match or (2) the first and second timing identifiersare not chronologically congruent.
 22. The non-transitory computerreadable medium of claim 20, wherein the instructions further cause themachine to: assign a first timestamp to the first watermark when thefirst watermark is detected; assign a second timestamp to the secondwatermark when the second watermark is detected; group the first andsecond watermarks to form the media detection event when an intervalbetween the first timestamp and the second timestamp is less than athreshold; and not group the first and second watermarks to form themedia detection event when the interval is greater than the threshold.23. The non-transitory computer readable medium of claim 22, wherein theinstructions further cause the machine not to group the first and secondwatermarks to form the media detection event when the first timestampmatches the second timestamp.
 24. The non-transitory computer readablemedium of claim 20, wherein the first watermark is embedded in the firstaudio stream based on a first watermarking technique, the secondwatermark is embedded in the second audio stream based on a secondwatermarking technique, and the instructions further cause the machineto (i) detect the first watermark based on the first watermarkingtechnique and (ii) detect the second watermark based on the secondwatermarking technique.
 25. The non-transitory computer readable mediumof claim 24, wherein the instructions further cause the machine todetect a third watermark embedded in the first audio stream based on thesecond watermarking technique, the third watermark embedded in the firstaudio stream based on the second watermarking technique.
 26. Thenon-transitory computer readable medium of claim 20, wherein theinstructions further cause the machine to: assign a first series ofwatermarks to a first monitoring track, the first series of watermarkslimited to watermarks embedded in the first audio stream based on afirst watermarking technique; and assign a second series of watermarksto a second monitoring track, the second series of watermarks includingwatermarks embedded in either the first audio stream or the second audiostream based on the first watermarking technique, both the first andsecond series of watermarks including the first watermark.
 27. Thenon-transitory computer readable medium of claim 26, wherein theinstructions further cause the machine to assign a third series ofwatermarks to a third monitoring track, the third series of watermarksincluding watermarks embedded in either the first audio stream or thesecond audio stream based on either the first watermarking technique ora second watermarking technique, the third series of watermarksincluding both the first watermark and the second watermark.
 28. Thenon-transitory computer readable medium of claim 20, wherein theinstructions further cause the machine to monitor the first and secondaudio streams simultaneously.